THE SYNTHESIS AND CHARACTERIZATION OF SOME STABLE CE-III BETA-DIKETONATE COMPOUNDS - X-RAY CRYSTAL-STRUCTURES OF [CE-2(ETBD)(6)(TETRAGLYME)] AND [NH4][CE(ETBD)(4)] [ETBD = 1-ETHOXY-4,4,4-TRIFLUOROBUTANE-1,3-DIONATE AND TETRAGLYME = CH3O(CH2CH2O)(4)CH3]

The cerium(III) beta-diketonate compounds [Ce-2(beta-diket)(6)(tetragl yme)] [beta-diket = etbd (1-ethoxy-4,4,4-trifluorobutane-1,3-dionate) 1, hfpd (1,1,1,5,5,5-hexafluoropentane-2,5-dionate) 2 and hfod ,2,3,3- heptafluoro-7,7-dimethyloctane-4,6-dionate) 3 and tetraglyme = CH3O(CH 2CH2O)(4)CH3] were synthesised from the reaction of CeCl3 . 7H(2)O and tetraglyme with an aqueous ethanolic solution of Na(beta-diket). The unusual reaction of cerium ammonium nitrate, [Ce(NH4)(2)(NO3)(6)], and Hetbd in an ammoniacal mixture of dimethoxyethane resulted in the amm onium cerium(III) salt, [NH4][Ce(etbd)(4)] 4, rather than the expected cerium(IV) species. All compounds were characterised by spectroscopic methods and in the cases of 1 and 4, also by X-ray crystallography. T he structure of [Ce-2(etbd)(6)(tetraglyme)] 1 consists of two Ce(etbd) (3) moieties bridged by a tetraglyme molecule. The two Ce atoms in thi s molecule are eight and nine coordinate respectively with distorted d ocahedral and monocapped square antiprismatic geometries. The crystal structure of 4 is stabilised by an extensive hydrogen bonding network involving the NH4+ cation and one oxygen atom from each of the four et bd ligands belonging to the [Ce(etbd)(4)](-) anion, with additional NH 4+... F3C(etbd) interactions. The Ce in the [Ce(etbd)(4)](-) anion is eight coordinate with a distorted square antisprismatic geometry. All the complexes are air and moisture stable, and-some compounds have goo d volatilities and thermal stabilities, as demonstrated by sublimation and TGA/DSC studies. (C) 1998 Elsevier Science Ltd. All rights reserv ed.